The purposes of this study are to identify and assess the etiological and environmental factors associated with the major idiopathic headache types, to investigate the association between headache symptoms and features, to explore the development of a new classification system of headache, to measure the prevalence, and to describe the demographic characteristics of the major types of headache. To this end a survey of the general population has been designed. The survey questionnaire, which includes sections on demography, descriptive headache features, medical information, and history, has been developed. The study consists of two parts: a feasibility study and an area survey. In the feasibility study, patients from four headache clinics have participated in a telephone interview. Information in the physician files about the headaches has also been abstracted. The data are now being analyzed and preliminary results show that the statistical technique of discriminant analysis can correctly classify most cases of headache into four major types on the basis of patient reported data. The planning and design of the area survey has been completed.